JP2012248555A - Workpiece division method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a workpiece division method capable of reducing device quality deterioration caused by adhesion of a scrap produced as a result of workpiece division and suppressing possibilities of hindering post steps.SOLUTION: A workpiece division method comprises: a laser beam irradiation step of forming a modifying layer inside a workpiece by irradiating the workpiece with a laser beam of a wavelength having permeability with respect to the workpiece; a tape sticking step of sticking an expanding tape to the workpiece before or after performing the laser beam irradiation step; and a division step of imparting an external force to the workpiece by expanding the expanding tape after performing the laser beam irradiation step and the tape sticking step and dividing the workpiece along the modifying layer. The division step is performed in an atmosphere in which an absolute humidity is higher than or equal to 9.5 g/m.

Description

  In the present invention, a laser beam having a wavelength that is transparent to a workpiece is irradiated to form a modified layer inside the workpiece, and then an external force is applied to the workpiece to individually process the workpiece. The present invention relates to a method for dividing a workpiece to be divided into chips.

  A wafer such as a silicon wafer formed on the surface by dividing a plurality of devices such as IC and LSI by a division line is divided into individual devices by a processing apparatus, and the divided devices are various types such as mobile phones and personal computers. Widely used in electrical equipment.

  A dicing method using a cutting device called a dicer is widely used for dividing the wafer. In the dicing method, a cutting blade having a thickness of about 30 μm made by hardening diamond or other superabrasive grains with metal or resin is cut into the wafer while rotating at a high speed of about 30000 rpm, and the wafer is cut. Divide into devices.

  On the other hand, in recent years, a condensing point of a laser beam having a wavelength (for example, 1064 nm) having transparency to the wafer is positioned inside the wafer corresponding to the division line, and the laser beam is irradiated along the division line. There has also been proposed a method in which a modified layer is formed inside a wafer, and thereafter an external force is applied to the wafer by an expanding device to cleave the wafer and divide it into individual devices (for example, Japanese Patent Application Laid-Open No. 2005-129607). reference).

  The formation of the modified layer by the laser processing apparatus can increase the processing speed as compared with the dicing method by the dicer, and relatively easily process even a wafer made of a material having high hardness such as sapphire or SiC. be able to. In addition, since the modified layer can have a narrow width of, for example, 10 μm or less, the amount of devices taken per wafer can be increased as compared with the case of processing by the dicing method.

JP 2005-129607 A JP 2007-189057 A

  However, after forming a modified layer inside the wafer by irradiating the laser beam, an external force is applied to the wafer by an expanding device and the wafer is divided into individual device chips. Will occur.

  When the divided waste adheres to the surface of the device, the quality of the device is deteriorated, and there is a problem in that the bonding and packaging in the subsequent process are supported. Particularly in a MEMS (Micro Electro Mechanical Systems) device that cannot be cleaned after dividing the wafer into device chips, the adhesion of the divided waste becomes a big problem.

  The present invention has been made in view of the above points, and the object of the present invention is to reduce deterioration in the quality of the device due to adhesion of divided scrap caused by the division of the work piece and to hinder the subsequent process. It is providing the division | segmentation method of the to-be-processed object which can suppress.

According to the present invention, there is provided a method for dividing a workpiece, wherein the workpiece is irradiated with a laser beam having a wavelength that is transmissive to the workpiece, and a modified layer is formed inside the workpiece. A laser beam irradiation step, a tape adhering step for adhering an expanded tape to a workpiece before or after performing the laser beam irradiation step, and after performing the laser beam irradiation step and the tape adhering step, A dividing step of applying an external force to the workpiece by expanding the expanded tape and dividing the workpiece along the modified layer, the dividing step including an absolute humidity of 9.5 g / m ³ or more A method for dividing a workpiece is provided, which is performed in the atmosphere described above.

  According to the dividing method of the present invention, there is sufficient moisture in the atmosphere when the workpiece is divided. Accordingly, the amount of adsorbed moisture on the expand tape and the workpiece surface is increased, and the electrical conductivity is improved, so that charging is prevented. As a result, it is possible to reduce the divided waste adhering to the surface of the device, and it is possible to reduce the risk of device quality deterioration due to the attachment of the divided waste and the trouble in the subsequent process.

It is a perspective view of the laser processing apparatus suitable for implementing the division | segmentation method of this invention. It is a block diagram of a laser beam irradiation unit. It is a perspective view explaining a tape sticking step. It is a partial cross section side view explaining a laser beam irradiation step. It is a perspective view of an expanding apparatus. It is sectional drawing explaining a division | segmentation step. It is a graph which shows the relationship between the relative humidity in 20 degreeC, and the silicon | silicone waste adhesion number.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, there is shown a schematic configuration diagram of a laser processing apparatus 2 suitable for forming a modified layer in the workpiece dividing method of the present invention.

  The laser processing apparatus 2 includes a first slide block 6 mounted on a stationary base 4 so as to be movable in the X-axis direction. The first slide block 6 is moved along the pair of guide rails 14 in the machining feed direction, that is, the X-axis direction, by the machining feed means 12 including the ball screw 8 and the pulse motor 10.

  A second slide block 16 is mounted on the first slide block 6 so as to be movable in the Y-axis direction. That is, the second slide block 16 is moved in the indexing direction, that is, the Y-axis direction along the pair of guide rails 24 by the indexing feeding means 22 constituted by the ball screw 18 and the pulse motor 20.

  A chuck table 28 is mounted on the second slide block 16 via a cylindrical support member 26, and the chuck table 28 can be moved in the X-axis direction and the Y-axis direction by the processing feed means 12 and the index feed means 22. . The chuck table 28 is provided with a clamp 30 that clamps an annular frame that supports the wafer sucked and held by the chuck table 28.

  A column 32 is erected on the stationary base 4, and a casing 35 for accommodating the laser beam irradiation unit 34 is attached to the column 32. As shown in FIG. 2, the laser beam irradiation unit 34 includes a laser oscillator 62 that oscillates a YAG laser or a YVO4 laser, a repetition frequency setting unit 64, a pulse width adjustment unit 66, and a power adjustment unit 68. .

  The pulse laser beam adjusted to a predetermined power by the power adjusting means 68 of the laser beam irradiation unit 34 is reflected by the mirror 70 of the condenser 36 attached to the tip of the casing 35 and further collected by the condenser objective lens 72. The light is applied to the optical device wafer 11 held on the chuck table 28.

  At the tip of the casing 35, an image pickup means 38 for detecting a processing region to be laser processed aligned with the condenser 36 in the X-axis direction is disposed. The imaging means 38 includes an imaging element such as a normal CCD that images the processing region of the optical device wafer 11 with visible light.

  The imaging means 38 further outputs an infrared irradiation means for irradiating the optical device wafer 11 with infrared rays, an optical system for capturing the infrared rays irradiated by the infrared irradiation means, and an electrical signal corresponding to the infrared rays captured by the optical system. Infrared imaging means including an infrared imaging device such as an infrared CCD is included, and the captured image signal is transmitted to a controller (control means) 40.

  The controller 40 includes a central processing unit (CPU) 42 that performs arithmetic processing according to a control program, a read-only memory (ROM) 44 that stores a control program, and a random read / write that stores arithmetic results. An access memory (RAM) 46, a counter 48, an input interface 50, and an output interface 52 are provided.

  Reference numeral 56 denotes a processing feed amount detection means comprising a linear scale 54 disposed along the guide rail 14 and a read head (not shown) disposed on the first slide block 6. Is input to the input interface 50 of the controller 40.

  Reference numeral 60 denotes index feed amount detection means comprising a linear scale 58 disposed along the guide rail 24 and a read head (not shown) disposed on the second slide block 16. The detection signal is input to the input interface 50 of the controller 40.

  An image signal picked up by the image pickup means 38 is also input to the input interface 50 of the controller 40. On the other hand, a control signal is output from the output interface 52 of the controller 40 to the pulse motor 10, the pulse motor 20, the laser beam irradiation unit 34, and the like.

  Referring to FIG. 3, there is shown a perspective view showing a state in which the semiconductor wafer 11 to be processed by the dividing method of the present invention is attached to the expanded tape T. The semiconductor wafer 11 shown in FIG. 3 is made of a silicon wafer having a thickness of 50 μm with the back surface 11b ground, and a plurality of division lines (streets) 13 are formed in a lattice shape on the front surface 11a. A MEMS (Micro Electro Mechanical Systems) device 15 is formed in each region partitioned by a plurality of division lines 13.

  The MEMS device 15 forms devices such as a pressure sensor, an acceleration sensor, and a gyroscope by forming a fine structure such as a cavity structure, a cantilever structure, and a comb tooth structure with a dielectric film having a thickness of several μm on a silicon substrate. It is also called a micromachine device. A notch 17 is formed on the outer periphery of the semiconductor wafer 11 as a mark indicating the crystal orientation of the silicon wafer.

  In carrying out the dividing method of the present invention, the back surface 11b of the semiconductor wafer 11 is attached to the expanded tape T, which is an adhesive tape having an outer peripheral portion attached to the annular frame F. As a result, the semiconductor wafer 11 is supported by the annular frame F via the expanded tape T.

  After the semiconductor wafer 11 is supported by the annular frame F via the expanded tape T in this way, in the laser beam irradiation step, the semiconductor wafer 11 is sucked and held on the chuck table 28 via the expanded tape T as shown in FIG. Then, the annular frame F is clamped and fixed by the clamp 30.

  After moving the chuck table 28 directly below the image pickup means 38, the image pickup means 38 picks up an image of the processing area of the semiconductor wafer 11, and in the first direction with the condenser 36 of the laser beam irradiation unit 34 that irradiates the laser beam. Image processing such as pattern matching for positioning with the expanding street 13 is executed, and alignment of the laser beam irradiation position is performed. Next, the chuck table 28 is rotated 90 degrees to align the streets 13 extending in the second direction orthogonal to the first direction and the light collector 28.

  When the alignment step described above is completed, the condensing point P of the pulsed laser beam having a wavelength that is transmissive to the semiconductor wafer 11 from the condenser 36 is aligned with the inside of the semiconductor wafer 11, and the pulsed laser beam is moved to the street. 13, while moving along the chuck table 28, the chuck table 28 is moved in the direction indicated by the arrow X <b> 1 in FIG. 4 at a predetermined feed rate to form the modified layer 19 inside the semiconductor wafer 11.

  After the reformed layer 19 is formed inside the semiconductor wafer 11 along all the streets 13 extending in the first direction, the chuck table 28 is rotated 90 degrees, and the second direction orthogonal to the first direction A similar modified layer 19 is formed inside the semiconductor wafer 11 along all the streets 13 extending in the direction. The modified layer 19 is formed as a melt rehardened layer.

  The laser processing conditions in this embodiment are as follows, for example.

Light source: YAG pulse laser Wavelength: 1064 nm
Average output: 1.0W
Condensing spot diameter: 1 μm
Repetition frequency: 100 kHz
Processing feed rate: 50 mm / s

  A dividing step of dividing the semiconductor wafer 11 into individual chips along the modified layer 19 using the expanding device (dividing device) 80 shown in FIG. 5 after forming the modified layer 19 as a starting point of the division on the semiconductor wafer 11. To implement.

  The expanding apparatus 80 shown in FIG. 5 includes a frame holding means 82 for holding the annular frame F, and a tape extending means 84 for expanding the dicing tape T attached to the annular frame F held by the frame holding means 82. Yes.

  The frame holding means 82 includes an annular frame holding member 86 and a plurality of clamps 88 as fixing means arranged on the outer periphery of the frame holding member 86. An upper surface of the frame holding member 86 forms a mounting surface 86a on which the annular frame F is mounted, and the annular frame F is mounted on the mounting surface 86a.

  The annular frame F placed on the placement surface 86 a is fixed to the frame holding means 86 by a clamp 88. The frame holding means 82 configured as described above is supported by the tape extending means 84 so as to be movable in the vertical direction.

  The tape expansion means 84 includes an expansion drum 90 disposed inside the annular frame holding member 86. The upper end of the expansion drum 90 is closed with a lid 92. The expansion drum 90 has an inner diameter that is smaller than the inner diameter of the annular frame F and larger than the outer diameter of the wafer 11 attached to the dicing tape T attached to the annular frame F.

  The expansion drum 90 has a support flange 94 integrally formed at the lower end thereof. The tape expanding means 84 further includes driving means 96 for moving the annular frame holding member 86 in the vertical direction. The driving means 96 is composed of a plurality of air cylinders 98 disposed on a support flange 94, and the piston rod 100 is connected to the lower surface of the frame holding member 86.

  The driving means 96 composed of a plurality of air cylinders 98 includes an annular frame holding member 86, a reference position where the mounting surface 86a is substantially the same height as the surface of the lid 92 which is the upper end of the expansion drum 90, and an expansion. It moves up and down between the extended position below the upper end of the drum 90 by a predetermined amount.

  A division step of the semiconductor wafer 11 performed using the expanding apparatus 80 configured as described above will be described with reference to FIG. In the dividing step of the present embodiment, the expanding device 80 is installed in the airtight space 74. A humidifying unit 76 is disposed in the airtight space 74. The humidifying unit 76 includes a humidifier and a hygrometer, and controls the humidifier based on the humidity measured by the hygrometer.

The airtight space 74 in which the expander 80 is installed is humidified by the humidifying unit 76, and the humidity is maintained at a predetermined value or higher. Preferably, the humidity above a predetermined value is 9.5 g / m ³ or higher in absolute humidity.

In the present embodiment, the expander 80 is installed in the airtight space 74 and the humidity in the airtight space 74 is managed, but the atmosphere of the room in which the expander 80 is installed has an absolute humidity of 9.5 g / m ³ or more. You may manage to become.

  As shown in FIG. 6A, the annular frame F that supports the semiconductor wafer 11 via the expanded tape T is placed on the placement surface 86 a of the frame holding member 86, and the frame holding member 86 is clamped by the clamp 88. Fix it. At this time, the frame holding member 86 is positioned at a reference position where the mounting surface 86 a is substantially flush with the upper end of the expansion drum 90.

  Next, the air cylinder 98 is driven to lower the frame holding member 86 to the extended position shown in FIG. As a result, the annular frame F fixed on the mounting surface 86a of the frame holding member 86 is also lowered, so that the expanded tape T attached to the annular frame F abuts on the upper end edge of the expansion drum 90 and mainly has a radius. Expanded in the direction.

  As a result, a tensile force acts radially on the semiconductor wafer 11 attached to the expanded tape T. When a tensile force acts radially on the semiconductor wafer 11 in this manner, the strength of the modified layer 19 formed along the streets 13 is reduced, so that the modified layer 19 serves as a starting point for the division of the semiconductor wafer 11. Are cut along the modified layer 19 and divided into individual semiconductor chips (devices) 15.

  The temperature in the airtight space 74 where the expander 80 is installed is kept at 20 ° C., the relative humidity is changed in the range of 36% to 70%, and the surface 11a of the wafer 11 divided into chips 15 is observed with a microscope. When the number of silicon scraps of 1 μm or more adhering to each chip 15 was counted, the result shown in the graph of FIG. 7 was obtained.

As is apparent from FIG. 7, it is observed that the number of silicon scraps deposited is reduced at 20 ° C. and a relative humidity of 55% RH or more. Therefore, it can be concluded that it is preferable to perform the dividing step at a relative humidity of 55% RH or more. Since the saturated water vapor density at 20 ° C. is 17.3 g / m ³ , 20 ° C. relative humidity of 55% RH or more is calculated to be 9.5 g / m ³ or more in absolute humidity.

  In the above-described embodiment, the example in which the silicon wafer 11 in which the MEMS device is formed as the workpiece is described has been described. However, the workpiece to which the division method of the present invention is applied is not limited to this, The same dividing method of the present invention applies to general semiconductor wafers formed from silicon, compound semiconductor wafers, optical device wafers employing sapphire or SiC as a substrate for crystal growth, and various wafers and substrates on which no devices are formed. It is applicable to.

  In the above-described embodiment, the laser beam irradiation step is performed after the tape attaching step shown in FIG. 3 is performed. However, the semiconductor wafer 11 is directly sucked and held by the chuck table 28, and the laser beam irradiation step is performed. You may make it implement the tape sticking step shown in FIG.

11 Semiconductor wafer 13 Scheduled division line (street)
15 Device T Expanding tape F Annular frame 19 Modified layer 28 Chuck table 36 Light collector 74 Airtight space 76 Humidification unit 80 Expanding device (dividing device)

Claims (1)

A method of dividing a workpiece,
A laser beam irradiation step of irradiating the workpiece with a laser beam having a wavelength that is transparent to the workpiece and forming a modified layer inside the workpiece;
Before or after performing the laser beam irradiation step, a tape adhering step for adhering an expanded tape to a workpiece;
After performing the laser beam irradiation step and the tape adhering step, a dividing step of applying an external force to the workpiece by expanding the expanded tape and dividing the workpiece along the modified layer, and Equipped,
The dividing step is performed in an atmosphere having an absolute humidity of 9.5 g / m ³ or more.

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